The long-range goals of this ongoing longitudinal study of midlife aging in women are to accurately quantify the associations of menopause with the development and progression of sleep apnea and diminished sleep quality and to identify factors that influence the associations. Understanding the role of menopause in the development of sleep apnea and diminished sleep quality has important clinical and public health significance. Sleep apnea and diminished sleep quality are associated with significant cardiovascular morbidity, depression, and decrements in daytime performance. Because menopause will become a persistent state in nearly every woman during her lifetime, even a small effect on sleep apnea and insomnia, the major sleep disorders, would translate into significant morbidity. Furthermore, if associations are causal, understanding whether hormone replacement therapy or other factors significantly modify a menopause-sleep disorder link may lead to interventions that could reduce the occurrence and severity of sleep disorders in mid- and later life. The proposed study is designed to: 1) Test the hypothesis that changes over the continuum of pre to post menopause increase the incidence and progression of sleep disordered breathing, adjusted for baseline age, body composition, and other potential confounders, 2) investigate the effects of change in body composition during midlife on associations of menopause and sleep apnea, 3) quantify the risk of insomnia, hypersomnia and diminished sleep quality attributable to early, middle and late perimenopause and post menopause, 4) investigate protective effects of hormone replacement therapy on sleep problems, and 5) investigate genetic vulnerability to diminished sleep quality during menopause. To accomplish these aims, we propose additional research on our unique longitudinal cohort of midlife women, with 7-15 years of previously collected polysomnographic and other data with a) new data collected from overnight in-laboratory protocols with polysomnography conducted at 4-year intervals on 621 women enrolled in the Wisconsin Sleep Cohort Study, b) new data collected semi-annually by in-home polysomnography and other procedures and monthly diaries on menstrual characteristics and sleep problems on a subset of 280 women over their pre to peri to post menopausal years.